Characteristics of adverse reactions due to subcutaneous allergen immunotherapy applied between 2011-2021: Single center experience.

Introduction: The aim of this study was to elucidate the incidence of local, large local and systemic reactions after subcutaneus immunotherapy (SCIT) injections in our clinic and to determine the characteristic features of these adverse reactions.

Materials and methods: A total of 6000 SCIT injections administered to 163 patients between January 2011 and December 2021 were retrospectively evaluated. The study population consisted of patients with allergic rhinoconjunctivitis who underwent SCIT due to pollen, house dust mite or cat allergy, or patients who underwent SCIT due to venom allergy. Demographic characteristics of the patients, diagnoses, allergen sensitivities, immunotherapy protocol applied, adverse reactions, and the characteristics of these reactions were recorded.

Result: Totally, 163 patients with a mean age of 36.8 ± 12.7 years were enrolled in this research. Sex distribution was as follows: 55.2% (n= 90) were females. During the study, 218 allergic reactions were detected in 83 patients. The incidence of adverse reactions per injection was 3.6%. The probability of developing an adverse reaction in a patient during the entire subcutaneous immunotherapy was 53.9%. Of the adverse reactions that developed, 94 (43.1%, n= 47) were observed locally while 56 (25.7%, n= 40) were large local reactions, and 68 (31.2%, n= 30) were systemic. Incidence of adverse reactions per injection were 1.5%, 0.9%, and 1.1% for local reaction, large local reaction, and systemic reaction, respectively.

Conclusions: The results of this analysis elaborated that subcutaneous immunotherapy is a safe and tolerable treatment modality. However, before initiating treatment, the benefits and risks should be evaluated. The risk of systemic reactions is quite low, but fatal anaphylaxis can occur, so physicians need to be aware of the potential risks.